Pressure Relief Valve HTF101 Delphi. Fuel injection pressure regulators directly affect your engine and vehicle performance and can be a major contributor or hindrance to fuel economy. Delphi fuel injection pressure regulators provide consistent and predictable fuel pressure for superior drivability. These regulators maintain the correct pressure from your tank to the injector for varied driving conditions, providing enhanced fuel control accuracy. Delphi fuel injection pressure regulators feature precisely manufactured internal valves, diaphragms, and springs for excellent performance, longer life, and improved durabilit.